This invention relates to a method of producing polyetherester monomer and cement dispersion agents (or cement dispersants). It has been known to produce polyetherester monomer as an intermediate product by an esterification reaction of polyalkyleneglycol with a closed end and unsaturated carboxylic acid and to copolymerize this polyetherester monomer with vinyl monomers which are copolymerizable therewith to obtain vinyl copolymers that can be used widely as a dispersant, an antistatic agent, an antifogging agent, an emulsifier or an adherent. In such applications, the quality of the monomer to be used in such a copolymerization reaction, and in particular the quality of polyetherester monomer, is known to significantly affect the quality of the produced vinyl copolymer serving as a dispersant, an antistatic agent, an antifogging agent, an emulsifier or an adherent. In other words, if the quality of polyetherester monomer obtained as the intermediate product is not sufficiently high, vinyl copolymers produced therefrom cannot function satisfactorily as a dispersant, an antistatic agent, an antifogging agent, an emulsifier or an adherent.
U.S. Pat. Nos. 4,962,173 and 5,362,829, for example, disclosed water-soluble vinyl copolymers having polyalkyleneglycol chain as a side chain serving as cement dispersants capable of providing a superior fluidity characteristic with a small slump loss to hydraulic cement compositions such as mortar and concrete. Such a water-soluble vinyl copolymer is usually produced by first preparing polyetherester monomer as an intermediate product by an esterification reaction of polyalkyleneglycol with a closed end and unsaturated carboxylic acid and then copolymerizing it with vinyl monomers capable of copolymerizing therewith. In this case, the quality as a cement dispersant of the water-soluble vinyl copolymer which is obtained is significantly dependent on the quality of the monomer, and in particular that of polyetherester monomer, that is used in the copolymerization reaction. In other words, if the polyetherester monomer serving as an intermediate product is of a poor quality, fluidity cannot be provided to a satisfactory manner to a hydraulic cement composition when the water-soluble vinyl copolymer obtained therefrom is used as a cement dispersant. The lowering with time of the fluidity which has been provided (slump loss) is large in such a case, and products obtained by hardening such a hydraulic cement composition have a low compressive strength.
As disclosed in Japanese Patent Publications Tokkai 11-71151, 2000-159882, 2000-159883 and 2000-212273, such polyetherester monomers as described above have conventionally been produced by using an organic solvent with a low boiling point such as benzene in an esterification reaction of polyalkyleneglycol with a closed end and unsaturated carboxylic acid. Use of such an organic solvent with a low boiling point is advantageous in that it is possible to obtain polyetheresters of a fairly high quality. On the other hand, the solvent which has been used for the reaction must be collected and the cost of equipment therefor adds to the total production cost of the polyetherester, or that of the vinyl copolymer to be used as the intermediate product and that of the water-soluble vinyl copolymers serving as a cement dispersant. In addition, the workers will be forced to work in an undesirable environment due to some of the properties of these substances.
It is therefore an object of this invention to provide a method of producing polyetherester monomer of a high quality without using a solvent.
It is another object of this invention to provide water-soluble vinyl copolymers capable of serving as a cement dispersant with improved properties, obtainable from such polyetherester monomer.
The present inventors discovered, as a result of work in view of the above objects, firstly that it is essentially important to use polyalkyleneglycol with a closed end of a high quality must be used as a starting material in order to obtain polyetherester monomers of a high quality. Polyalkyleneglycol with a closed end obtained by ring-opening addition reaction of alkylene oxide to a corresponding monohydroxy compound is usually used as the starting material and although such polyalkyleneglycol with a closed end obtained by a ring-opening addition reaction is produced industrially by a mass production process and stored until it comes to be used, that is, until polyetherester monomers are to be produced by an esterification reaction with unsaturated carboxylic acid, the present inventors also discovered that free acids which are mostly lower carboxylic acids such as formic acid, acetic acid and propionic acid are generated as by-products and remain, depending on the conditions of the ring-opening addition reaction and the refinement after the reaction. Similar free acids are generated and remain, depending in particular on the conditions at the time of the storage, and polyetherester monomers of a high quality cannot be produced from such polyalkyleneglycol with a closed end if the concentration of the residual free acids exceeds a certain minimum value.
As a result of further investigations, it was discovered that polyetherester monomers of a high quality can be obtained by an esterification reaction between polyalkyleneglycol which h as been refined such that the concentration of residual free acids (converted to acetic acid) is less than a specified value and unsaturated carboxylic acid under a specified condition in the absence of any solvent and presence of a specified amount of p-benzoquinone and/or phenothiazine. The present inventors also discovered that water-soluble vinyl copolymers obtained by a radical copolymerization reaction of such polyetherester monomers of a high quality with vinyl monomers which are copolymerizable therewith inside a water solution can be used as a cement dispersant with superior quality.
This invention relates, on one hand, to a method of producing polyetherester monomer, shown by Formula 3 given below, through an esterification reaction of polyalkyleneglycol with a closed end, shown by Formula 1 given below, with the concentration of residual free acid (converted to acetic acid) less than 0.03 weight % and unsaturated carboxylic acid, shown by Formula 2 given below, in the absence of any solvent and under a heated and reduced-pressure condition in the presence of p-benzoquinone and/or phenothiazine in an amount corresponding to 0.03-0.5 weight % of the polyalkyleneglycol with a closed end, by using an acid catalyst and distilling away generated water:
R1xe2x80x94Oxe2x80x94Axe2x80x94OHxe2x80x83xe2x80x83(Formula 1)

where R1 is alkyl group with 1-22 carbon atoms, benzyl group, phenyl group or alkylphenyl group having alkyl group with 1-12 carbon atoms, R2 and R3 are each H or methyl group, and A is residual group obtained by removing all hydroxyl groups from polyalkyleneglycol of which the repetition number of oxyalkylene units (consisting either only of oxyethylene units or of both oxyethylene units and oxypropylene units) is 5-250. This invention relates, on the other hand, to cement dispersants characterized as comprising water-soluble vinyl copolymer obtained by a radical copolymerization reaction of polyetherester monomer produced by a method described above and vinyl monomers that can be copolymerized therewith.
Next, a method of producing polyetherester monomers of this invention will be explained. According to this invention, use is made of polyalkyleneglycol with a closed end shown by Formula 1 which has been refined such that the concentration of residual free acid (converted to acetic acid concentration) is less than 0.03 weight %, preferably less than 0.015 weight % and even more preferably less than 0.01 weight %. As explained above, polyalkyleneglycol with closed end is obtained by a ring-opening addition reaction of alkylene oxide with corresponding monohydroxy compound but lower carboxylic acids such as formic acid, acetic acid and propionic acid are produced as residual acid and remain in polyalkyleneglycol with a closed end thus obtained as a reaction product of ring-opening addition reaction, depending on the conditions at the time of the ring-opening addition reaction and the conditions of refinement after the ring-opening addition reaction. In particular, similar residual acids are generated as by-products, depending on the conditions under which it is stored. If the concentration of the residual free acids (converted to acetic acid) exceeds 0.03 weight %, polyetherester monomers with a high quality cannot be obtained by an esterification reaction of such polyalkyleneglycol with a closed end with unsaturated carboxylic acid shown by Formula 2. According to this invention, therefore, use is made of polyalkyleneglycol with a closed end refined such that the concentration of residual free acid (converted to acetic acid) is less than 0.03 weight %, preferably less than 0.015 weight % and more preferably less than 0.01 weight % for an esterification reaction with unsaturated carboxylic acid shown by Formula 2. Throughout herein, the concentration of residual free acid converted to acetic acid means the measured value measured by the method according to JIS(Japanese Industrial Standard)-K1503.
Examples of the method of refinement for removing residual free acids include (1) method by using an adsorbent, (2) methods by neutralization, and (3) method by salting off and dehydration after neutralization. Among these, the methods by using an adsorbent are preferred. Many kinds of such adsorbents may be mentioned but it is preferable to use an adsorbent containing aluminum oxide and/or magnesium oxide such as aluminum oxide-containing agents, magnesium oxide-containing agents, aluminum oxide-magnesium oxide-containing agents, silicate-aluminum oxide-containing agents and silicate-magnesium oxide-containing agents. There are also different kinds of methods for using such agents for a refining process. Preferable among them is a method of mixing polyalkyleneglycol with a closed end containing more than 0.03 weight % (converted to acetic acid) of residual free acid with an adsorbent under a heated condition at about 100xc2x0 C. and thereafter filtering away the mixture by applying pressure to obtain refined polyalkyleneglycol with a closed end as a filtered liquid with less than 0.03 weight % (converted to acetic acid) of residual free acid.
Regarding polyalkyleneglycol with a closed end shown by Formula 1 thus refined, examples of R1 include (1) alkyl groups with 1-22 carbon atoms such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, hexyl group, octyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group, eicosanyl group and docosanyl group; (2) benzyl group; (3) phenyl group; and (4) alkylphenyl groups having alkyl group with 1-12 carbon atoms such as methylphenyl group, ethylphenyl group, propylphenyl group, isopropylphenyl group, butylphenyl group, hexylphenyl group, octylphenyl group, nonylphenyl group and dodecylphenyl group. Among these, however, alkyl groups with 1-12 carbon atoms and benzyl group are preferable and alkyl groups with 1-3 carbon atoms are even more preferable.
As for A in Formulas 1 and 3, examples thereof include (1) residual groups obtained by removing all hydroxyl groups from polyethyleneglycol of which the oxyalkylene units are all oxyethylene units and (2) residual groups obtained by removing all hydroxyl groups from polyethylene-polypropyleneglycol of which the oxyalkylene units include both oxyethylene units and oxypropylene units. Among these examples, residual groups obtained by removing all hydroxyl groups from polyethyleneglycol are preferred.
If residual groups obtained by removing all hydroxyl groups from polyethylene-polypropyleneglycol are used as A, the repetition of its oxyethylene and oxypropylene units may be by random and/or block connections. The repetition number of the oxyalkylene units in the residual group representing A is 5-250, and is preferably 7-90.
Examples of polyalkyleneglycol with a closed end shown by Formula 1 include methoxy polyethyleneglycol, methoxy polyethyleneglycol-polypropyleneglycol, ethoxy polyethyleneglycol, ethoxy polyethyleneglycol-polypropyleneglycol, propoxy polyethyleneglycol, propoxy polyethyleneglycol-polypropyleneglycol, butoxy polyethyleneglycol, lauryloxy polyethyleneglycol, butoxy polyethyleneglycol-polypropyleneglycol, benzyloxy polyethyleneglycol, benzyloxy polyethyleneglycol-polypropyleneglycol, phenoxy polyethyleneglycol, phenoxy polyethyleneglycol-polypropyleneglycol, alkylphenoxy polyethyleneglycol, and alkylphenoxy polyethyleneglycol-polypropyleneglycol.
Examples of unsaturated carboxylic acid shown by Formula 2 include methacrylic acid, acrylic acid and crotonic acid. Among these, methacrylic acid is preferred.
According to this invention, polyetherester monomer shown by Formula 3 is obtained by causing polyalkyleneglycol with a closed end shown by Formula 1 which has been refined such that the concentration of residual free acid (converted to acetic acid) is less than 0.03 weight % and unsaturated carboxylic acid shown by Formula 2 as explained above to undergo an esterification reaction by using an acid catalyst under a heated and reduced-pressure condition in the absence of solvents and in the presence of p-benzoquinone and/or phenothiazine while distilling away generated water. The amount of p-benzoquinone and/or phenothiazine to be present in this reacting system should be 0.03-0.5 weight %, and preferably 0.1-0.25 weight %, of polyalkyleneglycol with a closed end shown by Formula 1. In particular, the presence of p-benzoquinone in an amount of 0.1-0.25 weight % of polyalkyleneglycol with a closed end shown by Formula 1 is preferable. If the amount of p-benzoquinone and/or phenothiazine present in the reacting system is less than 0.03 weight % of polyalkyleneglycol with a closed end shown by Formula 1, there is not sufficient effect on prevention of polymerization. If it is greater than 0.5 weight %, on the other hand, the effect is sufficiently strong but the radical copolymerization reaction does not proceed smoothly when the polyetherester monomer thus obtained is used as an intermediate product to produce vinyl copolymers.
The heating at the time of the aforementioned esterification reaction should preferably be to the temperature range of 105-135xc2x0 C. and the pressure in the range of 15-0.5 kPa. The heating and the lowering of the pressure should preferably be carried out either continuously or in a stepwise manner within the ranges given above.
Examples of the acid catalyst to be used in the esterification reaction include sulfiric acid, p-toluene sulfonic acid, phosphoric acid and methane sulfonic acid. They may be used either singly or as a mixture but it is preferable to use sulfiric acid singly or a mixed acid of sulfuric acid and p-toluene sulfonic acid. The amount of the acid catalyst to be used is preferably 0.2-1.5 weight % of the total of polyalkyleneglycol with a closed end shown by Formula 1 and unsaturated carboxylic acid shown by Formula 2.
The ratio between the amounts of polyalkyleneglycol with a closed end shown by Formula 1 and unsaturated carboxylic acid shown by Formula 2 to be used in the esterification reaction should preferably be 1/1.5-1/7 (in molar ratio). After the esterification reaction, the excess portion of unsaturated carboxylic acid is distilled away.
The method of producing polyetherester monomer according to this invention is explained next further in detail. When methoxy polyethyleneglycol methacrylate, for example, is produced as the polyetherester monomer of this invention, methoxy polyethyleneglycol and an excess amount of methacrylic acid are placed inside a reactor and a specified amount of p-benzoquinone and/or phenothiazine serving as a polymerization inhibitor, appropriate for the amount of the methoxy polyethyleneglycol which has been refined such that the concentration of residual free acid (converted to acetic acid) is less than 0.03 weight % and a specified amount of concentrated sulfuric acid serving as an acid catalyst are added into the reactor. Next, the temperature of the reacting system is gradually raised and its pressure is gradually lowered until a specified temperature-pressure condition is reached. An esterification reaction is carried out under this temperature-pressure condition while water which is generated is removed by azeotropic distillation of water and methacrylic acid. After the esterification reaction, the excess portion of methacrylic acid is removed to obtain methoxy polyethyleneglycol methacrylate. The polyetherester monomer thus obtained contains the aforementioned polymerization inhibitor and acid catalyst but it may be directly used as an intermediate product for the production of vinyl copolymers without refining to remove them.
Next, cement dispersants according to this invention will be described. The cement dispersants of this invention are characterized as comprising water-soluble vinyl copolymers obtained by a radical copolymerization reaction between polyetherester monomers obtained as explained above and vinyl monomers which are copolymerizable with them in an aqueous solution. Examples of such vinyl monomer include ethylenic unsaturated monocarboxylic acids and/or their salts, ethylenic unsaturated dicarboxylic acids and/or their salts, ethylenic unsaturated monocarboxylic acid esters, unsaturated carboxylic acid esters with hydroxyl group, aromatic vinyl monomers, vinyl monomers with amino group, vinyl monomers with amide group, vinyl monomers with aldehyde group, vinyl monomers with nitrile group, vinyl esters, alkene compounds, dien compounds and vinyl monomers having sulfonic acid group. Among these, ethylenic unsaturated monocarboxylic acids and/or their salts and vinyl monomers with sulfonic acid group are desirable. Particularly preferable are (1) (meth)acrylic acids and/or their salts such as (meth)acrylic acid, alkali metal salts of (meth)acrylic acid, alkali earth metal salts of (meth)acrylic acid and organic amine salts of (meth)acrylic acid, and (2) methallyl sulfonic acid salts to be used with such (meth)acrylic acids and/or their salts such as alkali metal salts of methallyl sulfonic acid, alkali earth metal salts of methallyl sulfonic acid and organic amine salts of methallyl sulfonic acid.
The invention does not impose any particular limitation on the copolymerization ratios of polyetherester monomer and vinyl monomers which are copolymerizable therewith but in the case of radical copolymerization of polyetherester monomer and (meth)acrylic acid and/or its salt, it is preferable to copolymerize 5-50 molar % of polyetherester monomer with 50-95 molar % of (meth)acrylic acid and/or its salt (such that the total will be 100 molar %), while in the case of radical copolymerization of polyetherester monomer, (meth)acrylic acid and/or its salt and methallyl sulfonic acid salt, it is preferable to copolymerize 5-45 molar % of polyetherester monomer, 50-90 molar % of (meth)acrylic acid and/or its salt and 0.3-15 molar % of methallyl sulfonic acid salt (such that the total will be 100 molar %).
The radical copolymerization reaction itself can be carried out in a known manner such as described, for example, in Japanese Patent Publication Tokkai 8-290948. Water-soluble vinyl copolymer can be obtained, for example, by preparing an aqueous solution containing polyetherester monomer obtained as described above, vinyl monomers which are copolymerizable therewith and a chain transfer agent and causing a radical copolymerization reaction for 4-8 hours at reaction temperature of 50-90xc2x0 C. in a nitrogen environment by adding a radical initiator. Examples of chain transfer agent which may be used in this process include 2-mercaptoethanol, mercaptopropionic acid and mercaptoacetic acid. Examples of radical initiator include persulfates such as sodium persulfate, potassium persulfate and ammonium persulfate and water-soluble radical initiators such as 2,2xe2x80x2-azobis(2-amidinopropane) dihydrochloride.
The average numerical molecular weight (hereinafter Pullulan converted by GPC method) of the water-soluble vinyl copolymers thus obtained by radical copolymerization is preferably 3500-70000 and more preferably 5000-40000.
Cement dispersants embodying this invention which comprises the water-soluble vinyl copolymers may be used for many kinds of hydraulic cement compositions using not only cement but also a mixing material in a fine powder form as a binder, or mortar and concrete as typical examples. Examples of cement include different kinds of portland cement such as normal portland cement, high early portland cement and moderate heat portland cement, as well as many different kinds of blended cement such as portland blast-furnace slag cement, fly ash cement and silica pozzolan cement. Examples of mixing material in a fine powder form include lime stone powder, calcium carbonate, silica fume, blast-furnace slag powder and fly ash.
The rate at which the cement dispersants of this invention should be used is normally 0.01-2.5 weight parts and preferably 0.05-1.5 weight parts % (by solid component) for 100 weight parts cement or a combination consisting of cement and a powder material for mixing. Cement dispersants according to this invention are usually used by adding together with kneading water when hydraulic cement composition is to be prepared.
The method of producing polyetherester monomer embodying this invention is characterized in that no solvent is used in the esterification reaction of polyalkyleneglycol with a closed end shown by Formula 1 which has been refined such that the concentration of residual acid (converted to acetic acid) is less than 0.03 weight % and unsaturated carboxylic acid shown by Formula 2. As an important result of this, there is no need to collect any solvent after the esterification reaction is completed. Moreover, the method of this invention is capable of producing polyetherester monomer of a high quality shown by Formula 3. As will be described in detail below, polyetherester monomer with high esterification reaction rate can be obtained without abnormal increase in viscosity or generation of gel at the time of the esterification reaction. Water-soluble vinyl copolymers using high-quality polyetherester monomer produced by a method of this invention as an intermediate product exhibit desirable characteristics as cement dispersant. They can provide fluidity to hydraulic cement compositions with only a small slump loss and hardened products obtained from such hydraulic cement compositions have improved compressive strength.
The invention is described next by way of the following four ((1)-(4)) examples of method for producing polyetheresters embodying the invention.
(1) Method of obtaining polyetherester monomer (P-1) by mixing 2.0 moles of propoxypolyethyleneglycol (with repetition number of oxyethylene units equal to 12, hereinafter written as n=12) with 0.035 weight % of residual free acid (converted to acetic acid) and 6 g of aluminum oxide-magnesium oxide-containing adsorbent for 1 hour under a heated condition at 110xc2x0 C., using a filter aid to filter the mixture with pressure after it is cooled to 80xc2x0 C. and obtaining refined propoxypolyetheylglycol (n=12) with 0.002 weight % of residual free acid (converted to acetic acid) as the filtrate. Next, 1.0 mole of this propoxypolyethyleneglycol (n=12) and 2.0 moles of methacrylic acid are caused to undergo an esterification reaction in the presence of p-benzoquinone in an amount of 0.19 weight % of the propoxypolyethyleneglycol (n=12) at temperature of 125-130xc2x0 C. and pressure of 12-2.5 kPa by using sulfuric acid as catalyst in an amount of 0.23 weight % with respect to the total of the propoxypolyethyleneglycol (n=12) and methacrylic acid while generated water is distilled away, and the excess portion of methacrylic acid is thereafter distilled away.
(2) Method of obtaining polyetherester monomer (P-2) by mixing 2.0 moles of methoxypolyethyleneglycol (n=9) with 0.038 weight % of residual free acid (converted to acetic acid) and 6 g of aluminum oxide-magnesium oxide-containing adsorbent for 1 hour under a heated condition at 110xc2x0 C., using a filter aid to filter the mixture with pressure after it is cooled to 80xc2x0 C. and obtaining refined methoxypolyetheylglycol (n=9) with 0.003 weight % of residual free acid (converted to acetic acid) as the filtrate. Next, 1.0 mole of this methoxypolyethyleneglycol (n=9) and 3.5 moles of methacrylic acid are caused to undergo an esterification reaction in the presence of p-benzoquinone in an amount of 0.16 weight % of the methoxypolyethyleneglycol (n=9) at temperature of 125-130xc2x0 C. and pressure of 10-2.5 kPa by using sulfuric acid as catalyst in an amount of 0.50 weight % with respect to the total of the methoxypolyethyleneglycol (n=9) and methacrylic acid while generated water is distilled away, and the excess portion of methacrylic acid is thereafter distilled away.
(3) Method of obtaining polyetherester monomer (P-3) by mixing 2.0 moles of methoxypolyethyleneglycol (n=23) with 0.033 weight % of residual free acid (converted to acetic acid) and 8 g of aluminum oxide-magnesium oxide-containing adsorbent for 1 hour under a heated condition at 110xc2x0 C., using a filter aid to filter the mixture with pressure after it is cooled to 80xc2x0 C. and obtaining refined methoxypolyetheylglycol (n=23) with 0.003 weight % of residual free acid (converted to acetic acid) as the filtrate. Next, 1.0 mole of this methoxypolyethyleneglycol (n=23) and 3.6 moles of methacrylic acid are caused to undergo an esterification reaction in the presence of p-benzoquinone in an amount of 0.14 weight % of the methoxypolyethyleneglycol (n=23) at temperature of 125-130xc2x0 C. and pressure of 7-2.5 kPa by using sulfuric acid as catalyst in an amount of 0.32 weight % with respect to the total of the methoxypolyethyleneglycol (n=23) and methacrylic acid while generated water is distilled away, and the excess portion of methacrylic acid is thereafter distilled away.
(4) Method of obtaining polyetherester monomer (P-4) by mixing 2.0 moles of methoxypolyethyleneglycol (n=75) with 0.040 weight % of residual free acid (converted to acetic acid) and 8 g of aluminum oxide-magnesium oxide-containing adsorbent for 1 hour under a heated condition at 110xc2x0 C., using a filter aid to filter the mixture with pressure after it is cooled to 80xc2x0 C. and obtaining refined methoxypolyetheylglycol (n=75) with 0.003 weight % of residual free acid (converted to acetic acid) as the filtrate. Next, 1.0 mole of this methoxypolyethyleneglycol (n=75) and 3.0 moles of methacrylic acid are caused to undergo an esterification reaction in the presence of p-benzoquinone in an amount of 0.16 weight % of the methoxypolyethyleneglycol (n=75) at temperature of 125-130xc2x0 C. and pressure of 1.0-2.5 kPa by using a mixture of sulfuric acid and p-toluene sulfonic acid (with weight ratio of 5/2) as catalyst in an amount of 0.28 weight % with respect to the total of the methoxypolyethyleneglycol (n=75) and methacrylic acid while generated water is distilled away, and the excess portion of methacrylic acid is thereafter distilled away.
Next, the invention is described by way of the following eight ((5)-(12)) examples of cement dispersant embodying the invention:
(5) Cement dispersant comprising water-soluble vinyl copolymer (D-1) with average numerical molecular weight of 13000 obtained by radical copolymerization of aforementioned polyetherester monomer (P-1) and methacrylic acid at the ratio of 35/65 (in molar %) in an aqueous solution.
(6) Cement dispersant comprising water-soluble vinyl copolymer (D-2) with average numerical molecular weight of 9200 obtained by radical copolymerization of aforementioned polyetherester monomer (P-1), sodium methacrylate and sodium methallyl sulfonate at the ratio of 33/61/6 (in molar %) in an aqueous solution.
(7) Cement dispersant comprising water-soluble vinyl copolymer (D-3) with average numerical molecular weight of 16000 obtained by radical copolymerization of aforementioned polyetherester monomer (P-2) and methacrylic acid at the ratio of 35/65 (in molar %) in an aqueous solution.
(8) Cement dispersant comprising water-soluble vinyl copolymer (D-4) with average numerical molecular weight of 9800 obtained by radical copolymerization of aforementioned polyetherester monomer (P-2), sodium methacrylate and sodium methallyl sulfonate at the ratio of 33/61/6 (in molar %) in an aqueous solution.
(9) Cement dispersant comprising water-soluble vinyl copolymer (D-5) with average numerical molecular weight of 21000 obtained by radical copolymerization of aforementioned polyetherester monomer (P-3) and methacrylic acid at the ratio of 35/65 (in molar %) in an aqueous solution.
(10) Cement dispersant comprising water-soluble vinyl copolymer (D-6) with average numerical molecular weight of 13500 obtained by radical copolymerization of aforementioned polyetherester monomer (P-3), sodium methacrylate and sodium methallyl sulfonate at the ratio of 33/61/6 (in molar %) in an aqueous solution.
(11) Cement dispersant comprising water-soluble vinyl copolymer (D-7) with average numerical molecular weight of 32000 obtained by radical copolymerization of aforementioned polyetherester monomer (P-4) and methacrylic acid at the ratio of 35/65 (in molar %) in an aqueous solution.
(12) Cement dispersant comprising water-soluble vinyl copolymer (D-8) with average numerical molecular weight of 18500 obtained by radical copolymerization of aforementioned polyetherester monomer (P-4), sodium methacrylate and sodium methallyl sulfonate at the ratio of 33/61/6 (in molar %) in an aqueous solution.